Catalog Product FAQs
Where can I find an Analytical Data Sheet or Certificate of Analysis?
Supporting analytical information is reported in the Analytical Data Sheet (ADS) for each product. Catalog product ADS can be downloaded here. Due to the sensitive and confidential nature of custom peptides, Vivitide does not make this information available online for download as with the catalog products. Instead the ADS is included in each product's packaging. Should you need another copy, or more information, please contact us via email or phone.
What about the Safety Data Sheet?
The Safety Data Sheet (SDS) for each product may be found on each product's page as a PDF to download. In the cases where the SDS has not been loaded yet, is not online, or is a custom product, they may be obtained by request via phone or email. Complete physical, chemical, biological, pharmacological, or toxicological properties of the products are not known. The products are intended to be used by qualified professionals under proper laboratory safety practices in appropriate facilities.
What is the appearance of my peptide?
The physical state for peptides ranges from amorphous solid to crystalline powder. Some peptides will appear as a small disk at the bottom of the vial, others may appear fluffy or powdery, and other peptides may not seem visible at all. Particularly, peptides ordered in small quantities such as 0.1 mg or 0.5 mg, may not be visible, especially through an amber glass vial.
Note: Peptides supplied as white lyophilized (freeze-dried) powder can differ in visual appearance between vialed lots due to various components in the process. For example, during exposure to nitrogen flush, the peptides can settle in different patterns. The freezing cycle can also contribute to visual differences depending on the rate; a slower rate will compact the peptide into a dense form. During the drying process, more water may evaporate, leaving the very little peptide visible to the naked eye. The pressure applied in the process will differ from lot to lot as well. These possible scenarios may change the appearance of the white mass in the vial but does not change the amount of peptide contained in the vial.
What is peptide purity?
This is the percentage of peptide that is found in the correct sequence as opposed to truncated, deleted, or incomplete sequences that can arise from peptide synthesis. The purity is determined by high performance liquid chromatography (HPLC).
What leads to different salt forms of peptides?
Many catalog and custom peptides are present in the trifluoroacetate (TFA) salt form. Peptides are often purified by reverse-phase High Performance Liquid Chromatography (rHPLC) using a TFA buffer. The charge on a free amine in the peptide, either on the N-terminus or in a side chain, attracts the TFA counter ion. In some cases, TFA salt is not the preference and an alternate salt form is preferred. An additional step is done by using an ion exchange column to exchange the TFA salt with a preferred salt. Some examples of alternative salt forms are acetate (-OAc) or hydrochloride (HCl). Since converting from a TFA salt form to another salt form requires an additional step, there is often an additional small fee.
Can you explain the packaging of the Peptide Institute catalog products (bulk, -v, -s products)?
We carry the full line of quality products of the Peptide Institute of Osaka, Japan. Those that have a catalog number with a -v and -s suffix are packaged as net peptide and are in injection vials. The products without a suffix are "bulk" and packaged by gross weight.
Vialed (-v and -s) Products:
A peptide with constant weight is lyophilized and sealed under nitrogen in each vial. The net peptide weight is precisely determined by amino acid analysis after acid hydrolysis, HPLC analysis and/or UV absorption measurement, which is indicated clearly on the label of each vial. The indicated weight is only the net peptide molecule and does not include the weight of any additional constituents (water, acetic acid, and so on). For example, code 4002-v Bradykinin is described as follows:
PBK-4002-v Bradykinin (0.5 mg vial), M.W. 1060.2 g/mol
This indicates that each vial contains approximately 0.5 mg of bradykinin and the exact weight is indicated on the label (for example, 0.53 mg) and the instruction sheet (for example, 0.53 mg, 0.50 μmol). The weight is determined carefully and precisely by experts in our quality control department; therefore, we guarantee the quantity in each vial even if the content seems to be a small quantity.
A peptide solution of a known concentration can be constituted easily by injecting a given volume of a suitable solvent, indicated in the instruction sheet, into the vial using a calibrated syringe and dissolving the contents thoroughly. The peptide content in each vial is relatively small and accurately measured, therefore, the peptide should not be taken out of the vial to prepare a solution with a guaranteed concentration. The instruction sheet can be found on the last page of the ADS/COA.
The amorphous powder of each peptide is thoroughly dried over desiccant in vacuo and then weighed into a screw-capped bottle. Thus, the weight indicated on the label represents the gross weight of the amorphous powder, which includes the peptide as well as the accompanying water and acetic acid, if any. This is also called "gross" peptide. The amount of water and acetic acid in each amorphous powder is precisely determined by elemental analysis, Karl Fischer titration or gas chromatography. In some cases, peptides contain hydrochloride, trifluoroacetate, or ammonia instead of acetic acid. The observed value(s) of such accompanying constituent(s) is given in the structural formula of the respective peptide described in this catalog. For example, code 4002 Bradykinin is described as follows:
PBK-4002 Bradykinin (Bulk 100 mg)
M.W. 1060.2 • 120.10 • 54.05 g/mol
The total molecular weight of this amorphous powder is calculated to be 1234.4, which consists of 1060.2 for the net bradykinin molecule, 120.10 for two molecules of acetic acid and 54.05 for three molecules of water. This means that 100 mg of this powder contains net 85.9 mg of bradykinin molecules. Amounts of the accompanying water and acetic acid vary with the lot; the exact value in the purchased peptide is available on request. Given the hygroscopic nature of amorphous powder, precise weighing of a small quantity of peptide is not an easy task.